A coupler apparatus having a configuration in which a coupling element and a ground plane both having a tabular shape are arranged to face each other is known from Jpn. Pat. Appln. KOKAI Publication No. 2011-151763, Jpn. Pat. Appln. KOKAI Publication No. Hei 5-183311, and Jpn. Pat. Appln KOKAI Publication No. 2011-114705.
It is often the case that, when the coupler apparatus having the above-described configuration is mounted on a communication apparatus, a metal (which will be referred to as a neighboring metal hereinafter) such as a metal surface of a housing of the communication apparatus or a metal housing of another device mounted on the communication apparatus faces the ground plane.
Further, when the neighboring metal faces the ground plane in this manner, a current is induced in the neighboring metal with an operation of the coupler apparatus, and coupling characteristics may be deteriorated.
Under the circumstances, it has been desired to suppress a deterioration in coupling characteristics of the coupler apparatus even though the apparatus is used in a situation that the neighboring metal faces the ground plane.